Passband Filter Series Branch for Spurious Mode Suppression
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Solution Overview
Problem
Existing passband filters, particularly those using bulk acoustic wave resonators, suffer from spurious modes that generate degraded second-order harmonics within the passband, which are not attenuated and can degrade signal quality.
Innovation Solution
A passband filter design incorporating a series branch with a set of resonators and reactive components, such as inductors or capacitors, with resonant frequencies outside the passband to suppress spurious modes, ensuring their associated frequencies are outside the passband and the combined resonant frequency falls within the desired passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If bulk acoustic wave resonators are used in passband filters, then the filter can operate at radio frequencies, but spurious modes generate degraded second-order harmonics within the passband that cannot be attenuated
Solution Approach 1:
The patent applies this principle by intentionally introducing spurious modes from additional resonators at controlled frequencies outside the passband. These harmful spurious modes are converted into a beneficial tool for attenuating the degraded second-order harmonics generated by the main resonators, thereby improving overall filter performance while maintaining radio frequency operation
Solution Approach 2:
The patent introduces additional resonators as intermediary elements that generate spurious modes serving as a mediator between the main resonators and the degraded harmonics. These intermediary spurious modes interact with the degraded second-order harmonics to provide attenuation, effectively mediating the harmful interaction between main resonators and passband signal quality
2Measurement precision
If the resonant frequency of resonators is placed within the passband, then the filter achieves desired frequency response, but spurious modes associated with the resonant frequency fall within the passband and degrade signal quality
Solution Approach 1:
The patent segments the filter into multiple independent resonator circuits, each with distinct resonant frequencies. The main resonators are tuned to frequencies within the passband for accurate frequency response, while additional resonators are tuned to frequencies outside the passband. This segmentation allows each resonator to be independently optimized, enabling the main resonators to provide accurate passband response while additional resonators generate spurious modes for harmonic attenuation without interfering with passband signal quality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed design effectively suppresses spurious modes and harmonics, resulting in a cleaner signal with improved frequency response and reduced noise, enhancing the performance of radio-frequency filters.
Implementation Method 1
A passband filter design incorporating a series branch with a set of resonators and reactive components, such as inductors or capacitors, with resonant frequencies outside the passband to suppress spurious modes
Data Source
AI summary
According to the present disclosure, a passband filter is provided. The passband filter has a series branch, where the series branch comprises a set of one or more resonators having a resonant frequency sufficiently away from the passband of the filter such that spurious modes, of the set of one or more resonators, that are associated with the resonant frequency are outside of the passband of the filter; a set of one or more reactive components in series with the set of one or more resonators, the set of one or more reactive components having a resonant frequency sufficiently away from the passband of the filter such that the spurious modes of the set of one or more reactive components, that are associated with the resonant frequency are outside of the passband, and such that the resulting combined resonant frequency of the series combination of the set of one or more resonators and the set of one or more reactive components is within the passband of the filter.